Viscoelastic behavior of maize kernel studied by dynamic mechanical analyzer.

The creep recovery, stress relaxation, temperature-dependence and their frequency-dependence of maize kernel were determined within a moisture content range of 11.9% to 25.9% (w/w) by using a dynamic mechanical analyzer. The 4-element Burgers model was found to adequately represent the creep behavior of the maize seeds (R(2)>0.97). The 5-element Maxwell model was able to better predict the stress relaxation behavior of maize kernel than the 3-element Maxwell model. The Tg values for the maize kernels decreased with increased moisture content. For example, the Tg values were 114 °C and 65 °C at moisture content values of 11.9% (w/w) and 25.9% (w/w), respectively. The magnitude of the loss moduli and loss tangent and their rate of change with frequency were highest at 20.7% and lowest at 11.9% moisture contents. The maize kernel structure exhibited A-type crystalline pattern and the microstructure was found to expand with increase in moisture content.

Preparation and characterization of starch crosslinked with sodium trimetaphosphate and hydrolyzed by enzymes.

Crosslinked porous starch samples were produced by first crosslinking corn starch with sodium trimetaphosphate (STMP) and then partially hydrolyzing it with a mixture of α-amylase and glucoamylase. The granule morphology, porosity, swelling power, adsorption capacity, crystalline nature, molecular structure, melting and viscometric properties of these starch samples were measured and analyzed. The results showed that the porous starch which was crosslinked with 6% (w/w) STMP (ScPS-6) possessed remarkable superiority in terms of thermal and shear resistance among all the starch samples tested. The ScPS-6 also had the highest porosity and largest average pore diameter values. The swelling power of crosslinked porous starch was 56.3% lower than that of uncrosslinked porous starch. First order reaction kinetics equation was found to excellently (R(2) ≥ 0.99, average error = 6.03%) predict the experimental adsorption kinetics data of methylene blue for the crosslinked porous starch samples.

Effect of steam explosion on biodegradation of lignin in wheat straw.

The effect of steam explosion pretreatment on biodegradation of lignin in wheat straw was studied in this paper. Through experiments and analysis, 0.8MPa operation pressure and 1:20 wheat straw to water ratio are optimum for destroying lignin and the maximum of lignin loss rate is 19.94%. After steam explosion pretreatment, the wheat straw was retted by Trametes versicolor for 40 days. Biodegradation rate of lignin was tested and the maximum of 55.40% lignin loss rate was found on day 30. During the whole process of both steam explosion pretreatment and biodegradation, 75.34% lignin was degraded, without steam explosion the biodegradation of raw material the degradation rate of lignin was 31.23% only. FT-IR spectroscopy, TGA and SEM were used for further validating the results of biodegradation.